Chapter 7 - TV Measuring Range
57
106 V3.2
Figure 7-6 DVB-C select service
In this operating mode, the arrow keys have a dual function. After entry of a new channel, the menu
item
2.FUNCTION
is inverted. That means that the program list can be operated with the arrow
keys. To start the scan, first press the F5 key in order to activate the first function of the arrow keys.
The scan is then started by first tuning the measuring receiver to a channel at which the scan
should begin. Press the
↑
key to start the scan in the positive direction. Press the
↓
key to do the
same in the negative direction. When the band limit is reached, the scan continues at the other end
of the range. You can end the scan at any time by pressing
HOME
. “SCAN” is shown on the
display while the scan takes place.
DVB-C parameters
7.2.2.1.3
As soon as the receiver has completed the synchronization process, several parameters are shown
on the display. When LOCK appears, it means that the digital receiver is receiving a valid data
stream.
In contrast, UNLK means that either the quality of the signal that is present is insufficient, or that
the parameters of the receiver do not match, or that no DVB-C signal can be received at this
frequency.
Once the receiver has synchronized, the set modulation scheme and the associated symbol rate
are shown on the display.
BER measurement (Bit Error Rate)
7.2.2.1.4
The measurement of the bit error rate aids in the determination of the quality of a DVB signal. To
determine the bit error rate, the error correction mechanisms in the digital receiver are used. The
data stream is compared before and after correction and the number of corrected bits is determined
from that. This number is placed in a ratio to the total throughput of bits and the BER is calculated
based on that. For DVB-C, there is only one error protection mechanism (Reed-Solomon), i.e.,
there is only one bit error rate (BER) here.
The BER is shown on the display in exponential form.
The measuring depth can be shifted between 1•10
8
and 1•10
9
bits. For changing the measuring
depth at first the key
HOME
has to be pressed. Then the depth of the bit error rate measurement
can be set to 1•10
9
(1 billion) bits via the menu item
BER -> e-9
.